Abstract

Stress-induced changes in surface figure were measured by torquing the bimetallic (electrolysis nickel on aluminum) mirror to its mount in 1 ft. -lb. increments up to 16 ft. lb., measuring the surface figure with an automatic phase measuring interferometer and fringe analysis program using photographed interferograms. The maximum stress-induced change in surface figure contributes to the measured cryogenically induced change in surface figure. The bimetallic mirror was nickel deposited with 900 µm of electrolysis nickel. Increments of 0.5 mil of nickel are ground and polished from the face of the mirror before each room temperature and 100 K interferometric test. The results show a linear relationship between the differential nickel thickness between the front and rear of the mirror and the rms surface figure of the front face of the mirror, corresponding qualitatively to a simple model’s prediction.

© 1985 Optical Society of America